Code Quality: Implemented Breadcrumb

src/Files.App.Controls/BreadcrumbBar/BreadcrumbBar.Properties.cs

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+// Copyright (c) Files Community
+// Licensed under the MIT License.
+
+using CommunityToolkit.WinUI;
+
+namespace Files.App.Controls
+{
+	public partial class BreadcrumbBar : Control
+	{
+		[GeneratedDependencyProperty]
+		public partial FrameworkElement? RootItem { get; set; }
+
+		[GeneratedDependencyProperty]
+		public partial object? ItemsSource { get; set; }
+
+		[GeneratedDependencyProperty]
+		public partial object? ItemTemplate { get; set; }
+	}
+}

src/Files.App.Controls/BreadcrumbBar/BreadcrumbBar.cs

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+// Copyright (c) Files Community
+// Licensed under the MIT License.
+
+using Microsoft.UI.Xaml.Automation;
+using Windows.Foundation;
+
+namespace Files.App.Controls
+{
+	public partial class BreadcrumbBar : Control
+	{
+		// Constants
+
+		private const string TemplatePartName_RootBreadcrumbBarItem = "PART_RootBreadcrumbBarItem";
+		private const string TemplatePartName_EllipsisBreadcrumbBarItem = "PART_EllipsisBreadcrumbBarItem";
+		private const string TemplatePartName_MainItemsRepeater = "PART_MainItemsRepeater";
+
+		// Fields
+
+		private readonly BreadcrumbBarLayout _itemsRepeaterLayout;
+
+		private BreadcrumbBarItem? _rootBreadcrumbBarItem;
+		private BreadcrumbBarItem? _ellipsisBreadcrumbBarItem;
+		private BreadcrumbBarItem? _lastBreadcrumbBarItem;
+		private ItemsRepeater? _itemsRepeater;
+
+		private bool _isEllipsisRendered;
+
+		// Properties
+
+		public int IndexAfterEllipsis
+			=> _itemsRepeaterLayout.IndexAfterEllipsis;
+
+		// Events
+
+		public event TypedEventHandler<BreadcrumbBar, BreadcrumbBarItemClickedEventArgs>? ItemClicked;
+		public event EventHandler<BreadcrumbBarItemDropDownFlyoutEventArgs>? ItemDropDownFlyoutOpening;
+		public event EventHandler<BreadcrumbBarItemDropDownFlyoutEventArgs>? ItemDropDownFlyoutClosed;
+
+		// Constructor
+
+		public BreadcrumbBar()
+		{
+			DefaultStyleKey = typeof(BreadcrumbBar);
+
+			_itemsRepeaterLayout = new(this, 2d);
+		}
+
+		// Methods
+
+		protected override void OnApplyTemplate()
+		{
+			base.OnApplyTemplate();
+
+			_rootBreadcrumbBarItem = GetTemplateChild(TemplatePartName_RootBreadcrumbBarItem) as BreadcrumbBarItem
+				?? throw new MissingFieldException($"Could not find {TemplatePartName_RootBreadcrumbBarItem} in the given {nameof(BreadcrumbBar)}'s style.");
+			_ellipsisBreadcrumbBarItem = GetTemplateChild(TemplatePartName_EllipsisBreadcrumbBarItem) as BreadcrumbBarItem
+				?? throw new MissingFieldException($"Could not find {TemplatePartName_EllipsisBreadcrumbBarItem} in the given {nameof(BreadcrumbBar)}'s style.");
+			_itemsRepeater = GetTemplateChild(TemplatePartName_MainItemsRepeater) as ItemsRepeater
+				?? throw new MissingFieldException($"Could not find {TemplatePartName_MainItemsRepeater} in the given {nameof(BreadcrumbBar)}'s style.");
+
+			_rootBreadcrumbBarItem.SetOwner(this);
+			_ellipsisBreadcrumbBarItem.SetOwner(this);
+			_itemsRepeater.Layout = _itemsRepeaterLayout;
+
+			_itemsRepeater.ElementPrepared += ItemsRepeater_ElementPrepared;
+			_itemsRepeater.ItemsSourceView.CollectionChanged += ItemsSourceView_CollectionChanged;
+		}
+
+		internal protected virtual void RaiseItemClickedEvent(BreadcrumbBarItem item)
+		{
+			var index = _itemsRepeater?.GetElementIndex(item) ?? throw new ArgumentNullException($"{_itemsRepeater} is null.");
+			var eventArgs = new BreadcrumbBarItemClickedEventArgs(item, index, item == _rootBreadcrumbBarItem);
+			ItemClicked?.Invoke(this, eventArgs);
+		}
+
+		internal protected virtual void RaiseItemDropDownFlyoutOpening(BreadcrumbBarItem item, MenuFlyout flyout)
+		{
+			var index = _itemsRepeater?.GetElementIndex(item) ?? throw new ArgumentNullException($"{_itemsRepeater} is null.");
+			ItemDropDownFlyoutOpening?.Invoke(this, new(flyout, item, index, item == _rootBreadcrumbBarItem));
+		}
+
+		internal protected virtual void RaiseItemDropDownFlyoutClosed(BreadcrumbBarItem item, MenuFlyout flyout)
+		{
+			var index = _itemsRepeater?.GetElementIndex(item) ?? throw new ArgumentNullException($"{_itemsRepeater} is null.");
+			ItemDropDownFlyoutClosed?.Invoke(this, new(flyout, item, index, item == _rootBreadcrumbBarItem));
+		}
+
+		internal protected virtual void OnLayoutUpdated()
+		{
+			if (_itemsRepeater is null)
+				return;
+
+			_isEllipsisRendered = _itemsRepeaterLayout.EllipsisIsRendered;
+			if (_ellipsisBreadcrumbBarItem is not null)
+				_ellipsisBreadcrumbBarItem.Visibility = _isEllipsisRendered ? Visibility.Visible : Visibility.Collapsed;
+
+			for (int accessibilityIndex = 0, collectionIndex = _itemsRepeaterLayout.IndexAfterEllipsis;
+				accessibilityIndex < _itemsRepeaterLayout.VisibleItemsCount;
+				accessibilityIndex++, collectionIndex++)
+			{
+				if (_itemsRepeater.TryGetElement(collectionIndex) is { } element)
+				{
+					element.SetValue(AutomationProperties.PositionInSetProperty, accessibilityIndex);
+					element.SetValue(AutomationProperties.SizeOfSetProperty, _itemsRepeaterLayout.VisibleItemsCount);
+				}
+			}
+		}
+
+		internal bool TryGetElement(int index, out BreadcrumbBarItem? item)
+		{
+			item = null;
+
+			if (_itemsRepeater is null)
+				return false;
+
+			item = _itemsRepeater.TryGetElement(index) as BreadcrumbBarItem;
+
+			return item is not null;
+		}
+
+		// Event methods
+
+		private void ItemsRepeater_ElementPrepared(ItemsRepeater sender, ItemsRepeaterElementPreparedEventArgs args)
+		{
+			if (args.Element is not BreadcrumbBarItem item || _itemsRepeater is null)
+				return;
+
+			if (args.Index == _itemsRepeater.ItemsSourceView.Count - 1)
+			{
+				_lastBreadcrumbBarItem = item;
+				_lastBreadcrumbBarItem.IsLastItem = true;
+			}
+
+			item.SetOwner(this);
+		}
+
+		private void ItemsSourceView_CollectionChanged(object? sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
+		{
+			if (_lastBreadcrumbBarItem is not null)
+				_lastBreadcrumbBarItem.IsLastItem = false;
+
+			if (e.NewItems is not null &&
+				e.NewItems.Count > 0 &&
+				e.NewItems[e.NewItems.Count - 1] is BreadcrumbBarItem item)
+			{
+				_lastBreadcrumbBarItem = item;
+				item.IsLastItem = true;
+			}
+		}
+	}
+}